272 ON THE EXTINCT MAMMALIA OF 



The first phalanx is three and a half inches long ; the breadth of its proximal 

 end is thirty lines, and that of its distal end twenty-five lines. 



The second phalanx, from the centre of its opposite articular surfaces, is an inch 

 and a half long ; the breadth of the proximal end is twenty-eight lines, and that of 

 its distal end twenty-five lines. 



The third phalanx, broken on one side, has about the same form and proportions 

 as in the ordinary Horse. Along the anterior slope it measures two and a half 

 inches, and its extreme breadth has been about four and one-third inches. The 

 width of the articular surface has been about two and a quarter inches'; and the 

 diameter from before backward is one and a quarter inches. 



20. The upper end of a metacarpal and seven lower extremities of metacarpals and 

 metatarsals, like those of the common Horse, from the Niobrara River. They vary 

 slightly in relation of size. The carpal articular surface of the upper metacarpal 

 fragment measures twenty-six lines in width, and sixteen lines from before back- 

 ward. The phalangial articular surface of the largest of the lower fragments mea- 

 sures two inches wide and twenty lines from before backward on the median trochlear 

 ridge ; of the smallest of the lower fragments, twenty-one lines wide and seventeen 

 lines from before backward. 



21. Two pastern, three coronet, and two coffin bones, from the Niobrara River. 

 The pasterns are somewhat mutilated, and one is devoid of its upper epiphysis. 



They are rather smaller than that of the reconstructed foot, but are otherwise like 

 it. Their comparative measurements with that of the latter are as follow : 



Length in the axis. 

 Breadth of proximal end. 

 Breadth of distal end, . 

 Breadth of shaft at middle, 

 Breadth of proximal articulation. 



The coronets are considerably smaller than that of the reconstructed foot, and 

 may probably have pertained to one or other of the larger nipparions hereafter 

 to be indicated. They differ slightly in size and relations of diameter among them- 

 selves. One of them closely corresponds in form with that of the common Horse, 

 and that of the reconstructed foot ; the other pair are more transversely convex in 

 front. Their comparative measurements, together with that of the reconstructed foot 

 are as follow : 



Length through the axis, 

 Breadth between the upper lateral tubercles, 

 Breadth of proximal articular surface, 

 Breadth of distal articular surface. 



Lines. 



Lines. 



Lines 



. 39 



37 





. 29 







. 24i 





23J 



. 19 



18J 



17J 



. 26 







Lines. 



Lines. 



Lines. 



Lines 



18 



17 



16 



15 



28 



23 



24 



23 



25 



20 



22 



21 



25 



20 



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21 



